Known supply units normally comprise a splicing device whereby a trailing end portion of a first strip unwound off a running-out reel is joined to a leading end portion of a second strip unwound off a new reel.
Known supply units of the above type provide for splicing the strips either at the respective end portions or by overlapping the strips, and may be provided with compensating stores, located along the supply path, to feed the strip to the user machine during the splicing operation, which, depending on the type of splice, is performed by arresting the running-out strip at least at the unit itself.
Supply units normally comprise two splicing rollers located on opposite sides of the running-out strip and having respective variable-radius outer lateral surfaces to permit passage of the first strip when the rollers are arrested in a standby operating position, and to splice the two strips when the rollers are moved into a tangent operating position. One of the two splicing rollers is normally used as a casting roller for the second strip, i.e. the end portion of the second strip is placed on the lateral surface of the roller, and is brought into contact with the first strip more or less rapidly, depending on the presence of said compensating stores.
Though fairly reliable, supply units of the above type have several drawbacks limiting their use in conjunction with current user machines. That is, some supply units provide for splicing the end portions of the two strips, but require a compensating store for ensuring as accurate a splice as possible and so minimizing waste material. On the other hand, besides failing to ensure accurate splicing of the two strips, thus increasing the amount of waste material, supply units with no compensating stores also fail to provide for high-speed splicing, by the high traveling speed of the strips and the high degree of inertia of the reels subjecting the strips to longitudinal stress which more often than not results in tearing if not actual breakage of the strips.